🚀 go-pugleaf

In article <1993Jan24.050302.4130@nntpd2.cxo.dec.com>, m_herodotus@csc32.enet.dec.com (Mario Herodotus) writes...
> 
>--
>I was wondering how this would work...
> 
>I save an image using Photoshop's JPEG export. I later open the image using
>Photoshop's JPEG aquire and edit the image. I now save the new image using
>Photoshop's JPEG export again. Does the new image suffer more loss due to 
>compression a second time around? Does the new image have only the same 
>loss as the first time the original was saved? How would this affect an 
>image that is saved/opened several times with JPEG compression? Does it
>suffer more loss each time it is saved?
> 
>Thanks,
>Mario
> 
>--------------------------------------------------------------------------
>    I can't afford my own opinions, and DEC won't pay for them either.
>--------------------------------------------------------------------------
>Mario Herodotus  (CX03 1/K3)  |      m_herodotus@csc32.dec.com
>Digital Equipment Corporation |
>Customer Support Center       |  or  m_herodotus%csc32.dec@decwrl.dec.com
>305 Rockrimmon Blvd.          |
>Colorado Springs, CO 80919    |  or  ...!decwrl!csc32.dec.com!m_herodotus
>                              |
>(800) 354-9000  Ext 25520     |  or  CSC32::M_HERODOTUS
>[direct line (719) 592-5520]  |                       
>--------------------------------------------------------------------------

Mario, 

Imagine meeting you here on the Usenet :^).  Anyway, theoretically yes you 
will suffer image loss everytime you recompress the image.  Storm Technologies
recommends that you do all your editing on a Photoshop file, and then save it
as a JPEG file for archiving the file.  

Now for the pragmatic answer.  I have played around with doing this, and can't
notice any  degradation of the image even after 10 times (this is assuming that
you save  the image with a Q=90 value - I think that's the excellent value on
the PS  JPEG module).  When I played around with Q values of 75, I would get 
noticeable degradation of the image after a couple of saves.  I typically  only
use a Q value of 90 to maintain the quality of the image.  This still gives me
reasonable compression of the image (about 1/10th the size of the original). 
One thing I have noticed is that sometimes the JPEG file gets larger with every
save.  

Hope this helps.  

Jeff

yaplee@h2olog.seo.dec.com